The present invention relates to a process for the preparation of carboxyl compounds such as esters, lactones and carboxylic acids from the corresponding carbonyl compounds. More particularly it relates to a process for the preparation of lactones, and more especially still to a process for the preparation of caprolactone, by reaction of the corresponding ketones with hydrogen peroxide.
Lactones are in general prepared by oxidation of the corresponding cyclic ketones by means of percarboxylic acids. This technique, though very efficient, requires the preliminary preparation of the peracids, for example by direct oxidation of the corresponding aldehyde. Furthermore, the presence of the percarboxylic acids and of the corresponding carboxylic acids in the reaction mixture results in the formation of relatively large amounts of by-products derived therefrom.
In order to simplify the reaction scheme, it has been proposed, in British Pat. No. 1,050,846 filed on Sept. 16, 1964 in the name of Imperial Chemical Industries Ltd., to react a cyclic ketone, such as cyclohexanone, directly with hydrogen peroxide in the presence of a catalyst consisting of an oxyacid of an element of a long period of groups IV to VI of the periodic table of the elements. However, the amounts of catalyst employed are very high. Furthermore, the yields of caprolactone from this known process are very low, probably because of the formation of hydroxycaproic acid. This latter product, which cannot easily be converted to caprolactone, proves to be very troublesome if the caprolactone is used for the preparation of polymers such as polyesters, polyols and polyurethanes.